Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751443AbcLEIjS (ORCPT ); Mon, 5 Dec 2016 03:39:18 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:35791 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750849AbcLEIjQ (ORCPT ); Mon, 5 Dec 2016 03:39:16 -0500 From: Nicolai Stange To: Christian =?utf-8?Q?K=C3=B6nig?= Cc: Nicolai Stange , Alex Deucher , Daniel Vetter , , Subject: Re: [PATCH] drm/radeon: don't add files at control minor debugfs directory References: <20161203144700.2307-1-nicstange@gmail.com> <20161205072709.zcoja6eak2sjgd2k@phenom.ffwll.local> <5b8f4c38-c993-90af-5417-5e2e3cc38b58@amd.com> Date: Mon, 05 Dec 2016 09:39:12 +0100 In-Reply-To: <5b8f4c38-c993-90af-5417-5e2e3cc38b58@amd.com> ("Christian \=\?utf-8\?Q\?K\=C3\=B6nig\=22's\?\= message of "Mon, 5 Dec 2016 08:42:49 +0100") Message-ID: <87pol6ahxr.fsf@gmail.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id uB58dOKB016084 Content-Length: 5113 Lines: 104 Christian König writes: > Am 05.12.2016 um 08:27 schrieb Daniel Vetter: >> On Sat, Dec 03, 2016 at 03:47:00PM +0100, Nicolai Stange wrote: >>> Since commit 8a357d10043c ("drm: Nerf DRM_CONTROL nodes"), a >>> struct drm_device's ->control member is always NULL. >>> >>> In the case of CONFIG_DEBUG_FS=y, radeon_debugfs_add_files() accesses >>> ->control->debugfs_root though. This results in the following Oops: >>> >>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 >>> IP: radeon_debugfs_add_files+0x90/0x100 [radeon] >>> PGD 0 >>> Oops: 0000 [#1] SMP >>> [...] >>> Call Trace: >>> ? work_on_cpu+0xb0/0xb0 >>> radeon_fence_driver_init+0x120/0x150 [radeon] >>> si_init+0x122/0xd50 [radeon] >>> ? _raw_spin_unlock_irq+0x2c/0x40 >>> ? device_pm_check_callbacks+0xb3/0xc0 >>> radeon_device_init+0x958/0xda0 [radeon] >>> radeon_driver_load_kms+0x9a/0x210 [radeon] >>> drm_dev_register+0xa9/0xd0 [drm] >>> drm_get_pci_dev+0x9c/0x1e0 [drm] >>> radeon_pci_probe+0xb8/0xe0 [radeon] >>> [...] >>> >>> Fix this by omitting the drm_debugfs_create_files() call for the >>> control minor debugfs directory which is now non-existent anyway. >>> >>> Fixes: 8a357d10043c ("drm: Nerf DRM_CONTROL nodes") >>> Signed-off-by: Nicolai Stange >> Applied to drm-misc with Dave's irc ack, thanks for your patch. > > If it's still worth it the patch is Reviewed-by: Christian König > . > > On the other hand when ->control is always NULL, why do we still have > ->control anyway? Yes, I was wondering about that, too. Quoting from 8a357d10043c ("drm: Nerf DRM_CONTROL nodes"): Since I don't like dead uabi, let's remove it. But since this would be a really big change I think it's better to start out small by simply not registering anything. We can garbage-collect the dead code later on, once we're sure it's really not used anywhere. I'd too prefer compile time errors by purging ->control here. Daniel? > And BTW: Please double check the other drivers as well. # git grep '\->control' -- drivers/gpu/ drivers/gpu/drm/amd/amdgpu/amdgpu_device.c: adev->ddev->control->debugfs_root, drivers/gpu/drm/amd/amdgpu/amdgpu_device.c: adev->ddev->control); drivers/gpu/drm/amd/amdgpu/amdgpu_device.c: adev->ddev->control); Oops. drivers/gpu/drm/amd/amdkfd/kfd_dbgdev.c: ib_packet->control = (1 << 23) | (1 << 31) | drivers/gpu/drm/drm_drv.c: return &dev->control; That's drm_minor_get_slot(dev, type), but grepping for DRM_MINOR_CONTROL doesn't yield anything -> dead code. drivers/gpu/drm/gma500/psb_intel_sdvo.c: switch (sdvo->controlled_output) { drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS0; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS1; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= type; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB0; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB1; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS0; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS1; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output = 0; drivers/gpu/drm/i915/intel_sdvo.c: switch (sdvo->controlled_output) { drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS0; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS1; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= type; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB0; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB1; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS0; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS1; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output = 0; drivers/gpu/drm/msm/msm_debugfs.c: ret = late_init_minor(dev->control); Not an oops but dead code. drivers/gpu/drm/qxl/qxl_debugfs.c: qdev->ddev->control->debugfs_root, drivers/gpu/drm/qxl/qxl_debugfs.c: qdev->ddev->control); drivers/gpu/drm/qxl/qxl_debugfs.c: qdev->ddev->control); Oops. I'll send compile-only tested patches either tonight or tomorrow. Shall they cover the oopses only or the dead code as well? Thanks, Nicolai